The present invention, in some embodiments thereof, relates to monitoring and, more particularly, but not exclusively, to using EM radiation for monitoring changes of an internal biological tissue.
Medical instruments in which an echo of a pulse of EM radiation is used to detect and locate structures in the human body are known, see YOUNG, J. D et. al. Examination of video pulse radar systems as potential biological exploratory tools in LARSEN, L. E., and JACOBI, J. H. (Eds.): ‘Medical applications of microwave imaging’ (IEEE Press, New York, 1986), pp. 82-105, which is incorporated herein by reference. Such medical instruments includes microwave imaging devices, which may be referred to as tissue sensing adaptive radar (TSAR) or Imaging and other medical devices for detecting and possibly imaging internal biological tissues. The use of electromagnetic waves eliminates the need to expose the tissues to ionizing radiation, as performed during X-ray imaging, and to obtain relatively large tissue contrasts according to their water content.
One of the most common antennas which are used for such medical instruments is the well known biconic bow-tie antenna that maintains its port impedance and radiation pattern act in frequencies between certain limits where the low frequency is dictated by the size of the length of the cones and the upper limit by the port capacitance and feeding construction, see Antenna Theory, C. A. Balanis, 2 ed. John Willey, 1997 which is incorporated herein by reference. Such antennas usually suffer from a poor performance at relative low frequencies, where body electromagnetic penetration is better, and a planar construction that may be damaged due to electro-static discharges (ESD).
Such antennas have been used for detecting and imaging various pathologies, such as breast cancer. For example, U.S. Pat. No. 6,061,589 issued on May 20, 2000 describes a microwave antenna for use in a system for detecting an incipient tumor in living tissue such as that of a human breast in accordance with differences in relative dielectric characteristics. In the system a generator produces a non-ionizing electromagnetic input wave of preselected frequency, usually exceeding three gigahertz, and that input wave is used to irradiate a discrete volume in the living tissue with a non-ionizing electromagnetic wave. The illumination location is shifted in a predetermined scanning pattern. Scattered signal returns from the living tissue are collected and processed to segregate skin tissue scatter and to develop a segregated backscatter or return wave signal; that segregated signal, in turn, is employed to detect any anomaly indicative of the presence of a tumor or other abnormality in the scanned living tissue. The present invention is directed to a composite Maltese Cross or bow-tie antenna construction employed to irradiate the living tissue and to collect backscatter or other scatter returns.
In another example, U.S. Pat. No. 6,919,838 published on Jul. 19, 2005, describes a scanner or imager that employs a plurality of microwave transmitters that emit a multiplicity of pulses, which are received by a plurality of receivers. An object or person positioned between the transmitters and receivers can be scanned and subsequently imaged in extreme detail, due to the broad spectral content of the pulses. The scanner can be constructed as a stationary or portable device.